The mutual comparison of two or more comparison targets can be implemented by utilising a data network. The comparison target may for example be a product, a service, a travel destination, a person etc. The purpose of the comparison is to produce a final result, on the basis of which a target can be presented to a person performing the comparison from several possible comparison targets, which target best corresponds to the needs and desires of the person performing the comparison with regards to the properties used in the comparison, which describe the comparison target. Said comparison system is generally called a comparator.
FIG. 1a shows a one-dimensional evaluation line 1 and an opinion/evaluation 2 presented by a user about an evaluation statement presented in connection with some property. In the example in FIG. 1a the left end of the line illustrates a situation, where the comparator user agrees with the presented statement regarding an examined property. The right end of FIG. 1a illustrates a situation, where the comparator user completely disagrees with the presented statement. The evaluation given by the comparator user regarding the presented statement can be compared to several different comparison targets. By proceeding thus it is possible to calculate a congruency between the evaluation given by the comparator user and each comparison target, which congruency can be called an accuracy percentage.
In addition to a one-dimensional evaluation line, the comparator can also utilise a two-dimensional fourfold. A single question fourfold of the comparator consists of two properties to be examined, which are set perpendicularly against each other in the displayed fourfold. The properties to be compared with the aid of the question fourfold are in some way related to each other. Each property is in the question fourfold described for example with numerical values 0-100%. Any values can naturally be selected as the numerical values of the end points, for example −10 and +10. Alternatively the properties to be compared can be described with word pairs, e.g. disagree  agree, bad  good or unimportant  important.
FIG. 1b shows a principled model of a question fourfold 3 to be utilised in the comparator. The user of the question fourfold steplessly moves a response cursor 4 to a desired spot in the question fourfold 3. This stepless aiming possibility has been illustrated with four arrows pointing out from the cursor 4. When the response cursor 4 is according to the user in a spot, which corresponds to his opinion or evaluation with regards to the two properties shown in the fourfold, the user locks the response cursor 4 with a function related to the data processing device he uses.
In the examples in FIG. 1b the numerical value 0% of the horizontal axis of the fourfolds is situated in the left edge of the question fourfold and the numerical value 100% in the right edge of the question fourfold. Correspondingly the numerical value 0% of the vertical axis of the question fourfold is situated in the lower edge of the question fourfold and the numerical value 100% in the top edge of the question fourfold. What corresponds to a numerical value of 0% or 100% for each property is based on the definition made by the creator of the comparison procedure.
A person using the two-dimensional comparator sees two properties of the comparison target, one on the horizontal axis and one on the vertical axis. Generally the ends of the axes of the question fourfold describe opposite pairs of the same property. By using the two opposite pairs included in the question fourfold the comparator user can present his own evaluation of both examined properties by placing one evaluation point in a selected spot in the fourfold.
An example of a two-dimensional comparator is presented in U.S. Pat. No. 7,693,743. The patent presents a data collection and presentation method functioning in a data network, where a stepless two-dimensional data collection and presentation manner is utilised for collecting opinions and presenting the results of the inquiry. In the method according to the patent the operation is based on collecting evaluation data with the aid of a data network from persons selected by the person administrating the inquiry, the so-called inquiry creator, in two or more dimensions. The evaluation results of each evaluator are normalised per respondent, so that the average of the evaluation points of the evaluator entered into the fourfold is set in the origin and the deviation (standard deviation or some other value describing deviation) in a set standard value for each person performing the evaluation. With the described method the given responses can be scaled so that the evaluator's order of importance of different properties of the evaluation target are detected from the inquiry results, even if the responses given by some evaluator of the properties being evaluated were to be concentrated close together. Additionally the order of importance given to the properties by an individual evaluator can be scaled with the responses given by other participants in the inquiry. The scaled result can also be called a normalised result.
In the above-described examples the congruency of an evaluation given by a comparator user and one property of the target being evaluated can be expressed mathematically with the following expression:
                              A          =                                    [                              1                -                                                                                                                        X                        K                                            -                                              X                        E                                                                                                  N                                            ]                        *            100                          ,                            (        1        )            in which                N is an integer number, with which the axis of the question fourfold 3 (or the evaluation line 1) is divided into equally large parts (N is advantageously a number between 100 and 1000)        XK is the value of the user's response point between 0 and N        XE is the value of the response point of the target being evaluated between 0 and N and        A is the congruency of an evluation given by the comparator user and the property of the target being evaluated expressed as an accuracy percentage for one axis of the question fourfold or evaluation line.        
The total percentage S of the congruency of all evaluations given by the comparator user and all the properties of the target being evaluated is obtained with the equation:
                              S          =                                    ∑                              j                =                1                            n                        ⁢                                                  ⁢                                          A                j                            n                                      ,                            (        2        )            in which                S is the congruency percentage of all the responses        Aj is the congruency of axis jas an accuracy percentage and        n is the total number of axes included in the utilised fourfolds and/or evaluation lines.        
The comparator calculates the congruency of the evaluations of the comparator user and the properties of a certain comparison target using the equations (1) and (2). If necessary, the comparator calculates a corresponding congruency percentage illustrating the congruency for all comparison targets selected by the user.
A message-based online chat (Chat or LiveChat) implemented in a data network can also be utilised for comparing, marketing and selling articles and services. In the online chat a customer servant of the service provider and a possible buying customer engage in mutual text-based communication with the aid of their own data processing devices. The customer servant can with his own text-based messages guide the customer on the webpage by answering the questions posed by the customer or by posing his own specifying questions.
The online chat can be activated in many ways. There can for example be a button on the service provider's webpage, with which a customer on the webpage can invite a customer servant of the service provider to an online chat. Alternatively the customer servant can on his own offer online chat to a customer on the webpage. The decision about offering an online chat can be based on actions made by the customer on the service provider's webpage.